In Voice over Internet Protocol (VoIP) networks, packets arrive at the destination gateway or customer premises equipment (CPE) with packet delay variations, called jitter. When a network is exhibiting large amounts of variation in packet delay, it is exhibiting a correspondingly large amount of jitter. When packet delay is constant (i.e., substantially similar from packet to packet), jitter is low. Gateways and CPEs use de-jitter buffers to remove the packet delay variations and keep the received signal synchronized. De-jitter buffers are typically designed to buffer each arriving packet for a short interval to remove the effects of jitter from a decoded voice stream. De-jitter buffer performance directly impacts VoIP service quality. Misprovisioned or poorly designed de-jitter buffers can degrade VoIP call quality.
De-jitter buffers may be characterized as a fixed buffer or an adaptive buffer. A fixed buffer has a fixed buffer size. An adaptive buffer changes in size to reduce delay between receiving and transmitting a packet and/or to reduce the number of packets discarded when packets arrive too late to be buffered. If a packet loss event or an increase in jitter is detected, an adaptive buffer increases in size. If a decrease in jitter is detected, the adaptive buffer size decreases to reduce delay.